A terminal box for a solar cell panel is typically equipped with a bypass diode for short-circuiting the electric current generated by application of a reverse-direction voltage from one external-connection cable to the other external-connection cable when the electromotive force of the solar cell panel drops. When the by pass diode actually performs this function, a large electric current flows in the forward direction of the diode, so that the diode typically generates heat violently. This raises a possibility that the diode may be broken, or the lifetime of the diode may become considerably short, or the resin constituting the terminal box may be deformed with the heat generated by the diode to let the terminal box drop off from the solar cell panel. In particular, since the terminal box is used as long as twenty years or more in the outside in a state of being mounted on the solar cell panel, the possibility is high. Therefore, in view of the improvement in the long-term safety or reliability, it is demanded to prevent the temperature rise of the by pass diode effectively when the by pass diode is operating.
Conventionally, as means for preventing the temperature rise of the diode effectively, the means is generally adopted that allows the heat generated by the diode to escape to ambient atmosphere by arranging a heat dissipating plate or the like within the terminal box (Japanese Patent Application Laid-Open (JP-A) No. 2005-150277). To sum up, these means are those that aim at restraining the temperature rise of the diode by allowing the generated heat of the diode to be effectively dissipated.
On the other hand, in recent years, in accordance with the demand for increasing the output of the solar cell, a crystalline silicon solar cell is used more often than an amorphous silicon solar cell. However, since the output current of the crystalline silicon solar cell is larger by 30 times or more than that of the amorphous silicon solar cell, the amount of electric current that flows through the diode when the diode is operating, and subsequently the amount of generated heat, are considerably larger for the crystalline silicon solar cell than those of the amorphous silicon solar cell. Therefore, in a terminal box that is used in a crystalline silicon solar cell, one cannot fully restrain the temperature rise of the diode simply by using the conventional general means that merely allows the generated heat of the diode to be dissipated with use of a heat-dissipating plate or the like.